outboard motor problem

[tiawah53]

I have a 2003 40hp yamaha 4-stroke thats been a great motor, I'm having trouble. when in idle, idles freat but when i put in foward to go it dies imeditley. starts back up great but dies when you try to go.
i had new carburators "3" put on by yamaha dealer but didn't help. just wondering if anyone knows what might be the problem, Thanks, Frank

[boscoe99]

What was wrong with the old carburetors?

Was the problem the same before the new carburetors were installed?

Where are the old carburetors?

What is the dealer saying? Those are not cheap carburetors.

[tiawah53]

we took it to the local yamaha dealer while it was still under warranty cause of this problem, they had it along time & couldn't figure out the problem. they said the yamaha rep came by & told them to order a new carb assembly, it still did the same thing. we took it to a local outboard mech. and he found they had left out one bolt & had not hooked the linkage up to two of the carbs. he qas unable to find out the problem buy hes not a yamaha mech. he did tell us the choke is getting hot when you hold the key in to choke it.
as far as the old carbs knowing that place they probally put them on someone else's motor.Even though this motor is an 03 or 05, it has very little hours on it. I bought it in 09 still in the crate. the place "Jimmy Houston marine" they had switched to mercury dealer and had this one stored in the back.

[boscoe99]

I suggest that you find a mechanic that is knowledgeable of this model motor. The carburetors can be particularly fussy. All that any of us can do from a distance is to just guess.

I would suspect that the carburetors need to be dismantled and thoroughly cleaned in a heated ultrasonic cleaner, preferably using Yamaha carburetor dip. If the motor was under warranty from 2009 to 2012 and the carburetors were replaced during that time frame we are now mostly three years later. Carburetors, particularly those used in the F40, can foul in a very short period of time.

It might be a good idea to install slightly over size idle and main jets when reassembly the carburetors.

Use of a vacuumate device to synchronize the carburetors is highly desirable.

By the way, use of the push to choke function on the key switch does nothing at all with the F40 model. This motor uses a PrimeStart device for cold fuel enrichment and it is all automatic.